Summer temperature and precipitation govern bat diversity at northern latitudes in Norway

Abstract

This study investigated bat diversity in a temperature and precipitation gradient in fiord and valley landscapes of western Norway about 62° N. Equipment for automatic recording of bat calls was distributed in areas ranging from lowlands to alpine habitats with a mean July temperature range of 8-14°C. A general description of species distribution was given and diversity was analysed using both a generalised linear model (GLM) and a mixed-effects model (GLMM). With regard to the sampling design, the data were analysed on a binary scale, where presence or absence of any species other than the northern bat Eptesicus nilssonii is included. Models including temperature and precipitation explain 79% (GLM) to 91% (GLMM) of the overall variation in bat diversity. In sub-alpine and alpine areas with temperature below 10°C, only the northern bat was found. This species also forms maternity roosts where mean July temperatures are as low as 11°C and 10°C, below July temperatures found in the warmest areas beyond the Arctic Circle.